This used to be a legitimate solution to accommodating walk-ups when you don't have enough packs; however, with Discraft's rewording of the rule that "every player must buy a new full pack for $25 in order to be eligible for the grand prize," TDs should be careful in offering this option. In previous years I did just what you outlined above, and even had some couples play off a shared pack (each gets one disc and they can fight over the rest of the pack contents) by just adding a player to their pack for $10.

Of course, allowing those walk-ups would be the cool thing to do, but if word gets back to Discraft from a cranky player (especially if one of your "add-on" players ends up winning) that you broke the rules, your future events could be denied...my event was almost refused this year -- even after it had been scheduled -- because I was advertising that people could play for $10 if they had discs from a prior 2013 Ace Race (which is something else I've done for years).